There is a wide variety of different automatic swimming pool cleaners in use at the present time. Most of them are intended, and indeed designed, to move freely and randomly over the floor and wall surface of a pool in order to clean the entire surface area although there have been some designs in which a steering mechanism has been included with a view to modifying the uncontrolled random movement in order to make it more effective.
Nevertheless, for the most part, existing pool cleaners do not cover the entire surface area and patches, amounting quite commonly up to 30% of the surface area, are not covered by the pool cleaner during its supposedly “random” movement as a result of the fact that general patterns of movement tend to develop.
Numerous different reasons have been put forward to explain this failure. These include the fact that many pool cleaners become trapped against some or other formation in a swimming pool; the hose characteristics vary quite significantly and indeed hose sections can take on a particular crooked configuration in consequence of temperature fluctuations and physical forces that have been applied to the individual hose sections; the effective length of the hose may be incorrect and the hose may be too long or too short; and each different design of swimming pool and the location of the point of connection of the suction hose to the filtration assembly inhibits the swimming pool cleaner to a different extent and in different ways from reaching all regions of the surface.
A common partial cure that is recommended is to take the hose out of the pool; stretch it out in a straight line; and leave it in the sun for a time sufficient to enable it to totally relieve stresses in the plastic material from which it is made. Thereafter the hose should be cooled rapidly in the straight condition. This sometimes has a beneficial effect but by no means overcomes certain limitations that are inherent in some swimming pool installations and it also does not prevent the problem from recurring.